I'm an investor with over 15 years of experience and I don't have an LLC and I'm of the opinion that they are simply unnecessary 90% of the time.Do you have a business partner?

In a nutshell, bya) rigorous early weeding of applicants.b) only paying for credit check and deferring that till lastc) always knowing whether an application will be successful before the credit check staged) doing our own background checks.we are able to  refund unsuccessful applicants.For the avoidance of doubt if we haven't decided we can accept an application by the time it gets to the final stage (credit check) we reject it.

Form 3 (or more) LLC’s to avoid having all assets being subject to getting sued. 1 – An LLC as the buy and hold holding company, 2 – An LLC for flips, 3 – An LLC as the operating company (heads into contracts, collects rents, etc.).

I want to know what sort of procedure or check list I should follow in order to avoid such a situation.

If I did decide to flip it, how could I do so and avoid paying all of the taxes and liens on the front end?

You can (and should) also require that everyone over 18 years of age complete and application and each one pay the app fee.Again, number of people as a criteria should be avoided as it can be construed to illegally discriminate against families. 

To avoid paying the California LLC fee for my Colorado LLC, it was recommended I make my brother (Colorado resident/property manager/registered agent) the managing member with 0% equity in the LLC.Thanks in advance.

I avoid getting into low P&I payment notes for this very reason. 

As a real estate investor, you should communicate clearly up front to avoid any form of confusion.  

I understand the need for a seller to avoid buyers who are not serious, but they could easily keep marketing and accept back up offers during the 1st buyer's due diligence phase  in case the buyer flakes on them.